The present invention relates in general to an electrical capacitor, preferably a non-impregnated, self-curing capacitor which includes a roll of a dielectric paper and/or plastic foil provided with metal layers applied on the foil preferably by evaporation in vacuum, a housing enclosing the roll and a polyatomic gaseous or vaporous additive medium of a hydrocarbon compound enclosed in the housing to fill the interspaces between the metal layers of the roll.
A capacitor of this kind is known for example from the German publication No. 2,704,458. In this publication, an electrical capacitor is described whose wound body or roll is impregnated by means of a base liquid and with a mixture of two additives of which one consists of a halogenic liquid on basis of toluene or other compound which can be tolerated in a capacitor and which has electrically negative vapors at a high pressure. Such electronegative gaseous additives are capable of absorbing electrons and hence exhibit a quenching effect. The electronegative gases however have no effect on positive ions.
A similar arrangement of an electric capacitor is known from the British Pat. No. 2,084,798 describing an electric capacitor of metallized polypropylene films in which the wound body or roll is also impregnated by electronegative gas or by mixtures of electronegative gas and air and/or nitrogen. The application of the additives medium is made by means of filling oil which is saturated with the gaseous additive medium.